1. Field of Invention
The invention relates to an image forming device utilizing an electrophotography format such as an electrophotography copying machine, a laser printer, a facsimile or composite OA equipment thereof, and to an electrically conductive member used therein. More specifically, the invention relates to an image forming device in which a toner image formed on an image bearing body is primarily transferred onto an intermediate transfer belt and, thereafter, the toner image is secondarily transferred onto a recording medium such as a paper to obtain an image, and to an intermediate transfer belt.
2. Description of the Related Art
In an image forming device using an electrophotography format, a uniform charge is formed on an image bearing body which is a photoconductive photoreceptor comprising an inorganic or organic material, an electrostatic latent image is formed by an image signal modulated by laser light, and the electrostatic latent image is developed with an electrified toner to obtain a visualized toner image. Then, by electrostatically transferring the toner image onto a transfer material such as a recording paper via an intermediate transfer body or directly, a required regenerated image is obtained. In particular, as an image forming device adopting a format of primarily transferring a toner image formed on the image bearing body onto an intermediate transfer body, and further secondarily transferring a toner image on an intermediate transfer body onto a recording paper, the device disclosed in Japanese Patent Application Laid-Open (JP-A) No. 62-206567 is known.
Since an electrically conductive material formed of a thermoplastic resin such as a polycarbonate resin or PVDF (polyvinylidene fluoride) used in an image forming device adopting the intermediate transfer body format is inferior in mechanical property, belt deformation relative to stress at driving is great, and a transferred image of high quality cannot be stably obtained. In addition, an elastic belt with a reinforcing material therein in which a woven fabric of polyester and an elastic member are laminated has been proposed, but the problem of color slippage due to creep deformation of a belt material with time arises in some cases.
Accordingly, JP-A Nos. 5-77252 and 10-63115 propose an intermediate transfer belt in which an electrically conductive filler is disposed in a polyimide resin excellent in mechanical strength and heat resistance.
In an image forming device adopting the intermediate transfer body format, a charge upon primary transfer influences the potential on a photoreceptor surface, and insufficient electrification and a spot-like defect are generated in some cases. By using a belt-shaped intermediate transfer body having a large degree of design freedom, and arranging a photoreceptor and 1st-BTR (primary transferroll) in an offset position, the influence on the potential on a photoreceptor at primary transfer can be reduced. By offsetting, the transfer function exhibits a close relationship with the surface resistance of an intermediate transfer belt.
On the other hand, in a device performing printing treatment at a high speed, the problems of concentration scattering and spot-like defects occur.